Fluidic fitting with integral face seal

Abstract

A fitting for a fluidic coupling includes a tube assembly that includes an inner tube, an intermediate tube formed of a polymeric material and disposed over at least a portion of a length of the inner tube, and an outer tube formed of a metal and disposed over the intermediate tube. The inner tube has an inner tube endface and a first fluid channel. The intermediate tube includes an extruded portion having a length and an intermediate tube endface. The outer tube has an outer tube endface and an outer surface. First and second radial crimps are formed on the outer surface at first and second distances from the outer tube endface and extend for first and second axial lengths, respectively. The inner and outer tube endfaces are co-planar and the intermediate tube endface is separated from the inner and outer tube endfaces by the length of the extruded portion.

What is claimed is: 
     
       1. A fitting for a fluidic coupling, comprising:
 a tube assembly comprising:
 an inner tube having an inner tube endface and a first fluid channel; 
 an intermediate tube formed of a polymeric material and disposed over at least a portion of a length of the inner tube, the intermediate tube including an extruded portion having a length and an intermediate tube endface; and 
 an outer tube formed of a metal and disposed over the intermediate tube, the outer tube having an outer tube endface and an outer surface, a first radial crimp on the outer surface at a first distance from the outer tube endface and extending for a first axial length, and a second radial crimp on the outer surface at a second distance from the outer tube endface and extending for a second axial length, the outer tube endface being co-planar with the inner tube endface, the intermediate tube endface being separated from the inner tube endface and the outer tube endface by the length of the extruded portion. 
 
 
     
     
       2. The fitting of  claim 1  further comprising a retaining ring disposed on the outer tube at the first radial crimp. 
     
     
       3. The fitting of  claim 2  further comprising a compression screw having a first counterbore having a first hole having a first bottom surface and a first diameter that is greater than a diameter of the retaining ring in a relaxed state, the first counterbore having a first through-hole having a second diameter that is less than the diameter of the retaining ring and extending from the first bottom surface, the first bottom surface configured to contact the retaining ring when the compression screw is axially advanced over the tube assembly. 
     
     
       4. The fitting of  claim 3  further comprising a coupling body having a second counterbore having a second hole having a second bottom surface and a third diameter that is greater than a diameter of the outer tube, the second counterbore having a second through-hole extending from the second bottom surface and defining a second fluid channel, wherein the intermediate tube endface is in contact with the second bottom surface and the intermediate tube is under compression to thereby seal the first fluid channel to the second fluid channel. 
     
     
       5. The fitting of  claim 1  wherein the inner tube endface includes a polished surface. 
     
     
       6. The fitting of  claim 1  wherein the inner tube is formed of a glass. 
     
     
       7. The fitting of  claim 6  wherein the inner tube is a fused silica capillary. 
     
     
       8. The fitting of  claim 1  wherein the inner tube is formed of a metal. 
     
     
       9. The fitting of  claim 8  wherein the inner tube is a stainless steel tube. 
     
     
       10. The fitting of  claim 1  wherein the intermediate tube is formed of polyether ether ketone. 
     
     
       11. The fitting of  claim 1  wherein the outer tube is formed of stainless steel. 
     
     
       12. The fitting of  claim 1  wherein the length of the extruded portion of the intermediate tube is less than 0.50 mm. 
     
     
       13. A method of forming a fitting for a fluidic coupling, the method comprising:
 for a tube assembly comprising an inner tube having an inner tube endface and a fluid channel, an intermediate tube formed of a polymeric material and disposed over at least a portion of a length of the inner tube and having an intermediate tube endface, and an outer tube formed of a metal and disposed over the intermediate tube, the outer tube having an outer tube endface and an outer surface, the inner tube endface, intermediate tube endface and outer tube endface being coplanar with each other:
 forming a first radial crimp on the tube assembly over a first crimp length at a first distance from the outer tube endface to secure the inner tube, intermediate tube and outer tube to each other and to extrude a portion of the intermediate tube such that the intermediate tube endface is separated from the inner tube endface and the outer tube endface by an extrusion length; and 
 forming a second radial crimp on the tube assembly over a second crimp length at a second distance from the outer tube endface. 
 
 
     
     
       14. The method of  claim 13  wherein the first radial crimp has a radial depth and wherein the extrusion length is determined in part by the radial depth. 
     
     
       15. The method of  claim 13  wherein the extrusion length is determined in part by the first crimp length. 
     
     
       16. The method of  claim 13  wherein the extrusion length is determined in part by the first distance from the outer tube endface. 
     
     
       17. The method of  claim 13  further comprising polishing at least one of the inner tube endface, the intermediate tube endface and the outer tube endface prior to the forming of the first radial crimp.